Hydraulic ttjreine



Nov. 16 1926.

` L. F. MOODY HYDRAULI TUHBINE Original Filed May 16, 1921 2 Sheets-Sheet 1 Nov. 1e '1926. r

L. F. MOODY HYDRAULIC TURBINE Original Filed May 16. 1921 2 Sheets-Sheet 2 A .lawn/ H.HMHwwmwwwwnnwww 'Ttig/m www Patented Nov. 16, i925.

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HYDRALIC TRBINE.

Application filed May 16, 1921, Serial-No. 469,936. Renewed December 28, 192,3.

This invention relates to hydraulic turbines and particularly to turbines oiE moderate and high specific speed. rJ'he chief object of the invention is to improve the performance and etliciency or a turbine both under normal and part gate conditions by reducing the resistance to the flow and to the rotation of the runner.

A further object of the invention is to avoid corrosion of the runner vanes caused by areas or' low pressure in the flow along the rear surfaces of the vanes.

Further objects of the invention particularly in the formation ot the turbine parts to maintain the air spaces between the flow and the runner vane surfaces will appear from the following description talren in connection With the accompanying dran/ings in Which- Fig. 1 is a vertical sectional viev.'v of a portion of a turbine illustrating one embodiment or the invention.

Fig. 2 is a diagrammatic sectional view through the runner vanes.

Fig. 3 is a view similar to Fig. 2 illustrating a modilied form ot runner.

Figp is a vieu7 similar to Fig. 3 illustrating a further modii'ication.

Fig. et is a similar view illustrating a further modification, and

Fig. 5 is ay sectional view similar to lFig. l, but with portions indicated at different planes7 and illustrating a modiiication.

In the specific embodiment oi the-invention shown in the drawings the runner R of a turbine ol the reaction type has a vertical shaft 10 and a hub 11 tapering in the directiono the discharge. rlhe runner vanes 12 are diagonally inclined and extend across the passage 13. The flow entering by intake passage 14E, preferably ot the volute type, is given a Whirl and passes on through inclined guide vanes 15 and into the transition space 16 Where its Whirl is increased and it is turned toward the axial direction and passed through the runner R at high velocity. A top casting 17 carries a bearing` 18 for the shaft 10 and has a conical guiding surtace 19 forming the inner Wall of the transition space 16. The liow discharging from the runner E passes out through the dratt tube D, which may be of the type shown or have a central core extending up into proximity to the runner.

By employing a suiiiciently high velocity head in the Water entering the runner, the pressure head can be reduced to atmospheric orlovver, so that by providing the opening air Will iioiv into the space .in advance of the runner, itorrning a continuous body ot air through the central portion ot the runner surrounding its hub.

The runner vanes 12 are of simple contour ext-ending across the flow lines and they are preferably relatively fiat, deliecting the Water but little and causing but little change in the amount of the velocity ot the Water passing through them, as is consistent With the development of a comparatively low' torque and correspondingly high speed. rlhe flow considered relatively to the runner vanos may approach closely to the flow in an impulse turbine in which there is no change in the pressure head, and (in an axial oiv impulse ruimer) but little change in the relative velocity as the Water passes through the runner. :if the lioiv is permitted to part from the backs oi the runner vanes so as to remain in contact only With the faces of the vanes a reduction in surface friction will result by keeping the Water away from the back surfaces of the vane. rlhe result is increased efficiency and may be eiiected with little change in the velocity relations since the flow through a high speed, light torque runner involves little change in the amount of the velocity.

The driving faces of the vanes are helicoidal and of varying pitch as shown bv the successive angles a3, a2 and a kin Fig. The length of the blade tace is such that at any point ot' theblade tace the line 1X ot' intersection of the blade tace With a stream line surface passing through said surface is greater than the circumferential pitch in this stream line surface at the discharge end` ot the runner.

The separation of the now from the back surfaces ot the vanes 12 may be effected by the angle and contour ot the vane surfaces with relation to the HOW (Fig. 2) or the vanes may be providedwith a projecting lip 20 (Fig. 3) on the 4back oi each vane and close to the inflow edge. The spaces 21 at lill) the backs of the varies or at 22 at the backs oi? the vanes and below each of the lips 20 will then be lilled with air and the flow will be separated from these back surfaces not only reducing the surface 'friction but also avoiding pitting and corrosion or said surfaces, and each lip 2O willproduce a wide channel for the flow of air from the hub or tip to the entire length of the vane. When the flow is not permitted to leave these surfaces there is a decided tendency for the water to lower its pressure along them at such a rapid rate that the stream parts from the surface leaving eddying water in contact with the vane and creating backward iow and eddies and causing rapid corrosion and wear. In many cases it may be desirable to position this lip 2O near the vane center for instance as indicated at 20 in Fig. 3a. It may be noted that the action from the inlet edge oit the runner vane to the edge of the lip 20, Q0 where the waten separates from the back ot the vane is that of a reaction turbine, and that beyond this point the action is that of an impulse turbine, since there may be a pressure drop from the inlet edge of the vane to the point ol separation of the water from the vane,

the pressure beyond this point being constant.

A further advantage of the separation of the flow from the vane surfaces is the improvement of part gate eHiciencies due to the filling of the space behind each vane by air instead of water in an eddying, turbulent condition. ln furtherance of this advantage it may also be desirable to permit the-water to part from either one or both ot the walls oit the passage 13 in which the ruimer is located. For instance air may be introduced around the ruimer sha'lit by passages 25 and this will serve to supply the spaces behind the ruimer vanes and at rpart gate the iiow will be formed with a freeV surface surrounding the turbine axis, the space within this surface being filled with air and not with eddying water as would be the case without an air inlet. When there is no such air admission the water is obliged to fill the entire space even when this involves sudden enlargement of the streams cross-section, and under off-normal conditions o operation this causes eddies and backward flow at some points. -`/Vith air admission the water'can maintain its natural elocity and contract to the stream crosssection required by this velocity, thus adjusting the area of the stream cross-section to the amount ott water admitted, the remainder of the space within the enclosing walls being filled with air.

In many turbines of the ordinary reaction type it may be desirable to limit the admissio'ii ot air to certain w-conditions etoperation. For example, at small gate openings when there is a tendency for such turbines to develop a vortex at the axis, if air were introduced at this time and the water permitted to form a rotating mass having a free surface, a large part of the eddies which ordinarily exist during this part gate condition would be eliminated. A large portion of thevrunner which would ordinarily be dragged through the water would now move through the air with comparatively little windage loss. It has beenobserved, for example, in ordinary turbines'that in starting the turbine with the guide vanesonly slightly opened, the turbine will run at a higher speed while the draft tube remains iilled with air than will be the case after the air is completely discharged from the tube and the runner begins to operate entirely in water. At the instant the draft tube becomes filled with water a noticeable slowing down in speed oi the turbine results.V A. turbine operated at low gate opening has a natural tendency to run as an impulse turbine, and only the exclusion of air forces it to operate as a reaction turbine. In many cases, therefore, it will be advantageous to admit air to the runner up to some denite gate opening and beyond this point Vto close lthe air inlet and operate at larger gate openings as a reaction turbine. For this purpose the air inlet 25 may be provided with means such as valve 26 with connections to close the valve at some definite gate opening. For instance, these connections may comprise a cam c on arm a of the wicket gate yl5 moving the arm l) of valve 26 to control the valve. It will also be desirable to provide the air supply connections with check valves closing whenever the pressure of the water rises above atmospheric so as to prevent a backward flow into the air supply, and opening whenever the water pressure drops so as to draw f in air.

In the embodiment oit the invention shown in Fig. et the runner R has the rear lips 30 placed opposite the tips ot the Vpreceding vanes as indicated by lines Y) so that the parting of the water from the vane surfaces will take place only over the portionl point W here the runner is shrouded as a t 33 the shrouding may be formed tohave edges 34;v along orifices Z1 as shown completing the edges of the Vnozzles for the jets j and leaving these discharged jets en-V ara-y nee of n1 sides. rhs 'venes se are` Af shown modified for a relatively lower or moderate specific speed with the entrance edges 43 rounded to suit a wide variation of the relative angle of entrance of the flow.

ln the admission of air around the runner it may be desirable to provide an air space around the tips of the runner vanes either in addition to or instead of the central air supply around the hub. For instance in Fig. l an air supply passage may be provided having openings 51 leading into the turbine conduit adjacent the tips of the runner vanes. Such an air supply will maintain an air space 52 around the runner tips reducing friction and serving to supply air to the spaces at the backs of the vanes.V Such an air space will also aid in reducing wasteful eddying of the liow under part gate conditions and thus increase the efficiency of the turbine. ln Fig. 5 a modified form of turbine is shown in which the How enters by volute 55 and passes with a whirl through the fixed vanes 56 into transition space 57 wherein the whirling flow is turned toward the axial direction onto the runner R2 from which it discharges into draft tube D having a central core C extending into proximity with the runner. The flow to the runner is controlled by the plunger gate 58 sliding in the stay vane ring 56 and having the piston portion 59 moved by fluid pressure in spaces 60, 61. rlfhe shaft 62 of the runner R2 has a bearing 63 in cover 64 and passes down through a sleeve 65 suspended from the end 66 of the stationary cylinder 67. An air supply pipe 70 opens into the space 7l between the cover G6 and plunger gate 58 and this gate has a central opening 72 throughwhich the air is drawn around the sleeve 65 down to the runner vanes, forming a central air space for the whirling vortexV of the inflow in transition space 57. rlhis central air supply is particularly advantageous in this plunger gate type of turbine inpermitting the flow in the transition space to have a free surface 73 at the center. As the gate 5S is closed and the flow is restricted the water does not have to lill the transition space but passes therethrough as aV smooth annular stream with central free surfaces 73 within which arrangement. Passages similar to 50, with openings 5l, shown in Fig. l would be used for this purpose (as shown at 50, 51'), either in addition to Ior instead of the openings 72. By means of these openings the iiow would be permitted to spring clear of the outer wall, as shown at 732.

lt is desirable to regulate the entrance of air and to restrict it to a rate only suliicient to maintain continuous air spaces in and around the runner without causing an undue amount to enter into suspension in the water and to pass on with it. Air which becomes mixed with the water and flows away with it reduces the eectiveness of the draft tube to some extent.

Inv some'cases where the runner is placed below or near the tail water, a rise in the tail water level may tend to submerge the runner, and in such event the air supply may be closed and the turbine operated as a reaction turbine. Sometimes, however, where the entrance pressure is above atmospheric because of abnormally high tail water or for other reasons, it may be. advantageous to put pressure on the air .supply to raise it suliiciently above atmospheric to overcome the water pressure and to maintain the air spaces as desired.

When a central core is used in the draft tube as in Fig. 5, air may be admitted to the draft tube below the runner to form a central air space through a pipe or passage 7 O and opening` 72 shown in lines carried up through the core C, either in addition to or instead of the pipe 70 and openings 72. The air space thus supplied from below the runner will under part loa-d conditions usually extend upward into the runner, this action being promoted by the reversal of flow which occurs in most runners in the portion near the axis during part gate operation, the flow in this region then being upward. lThe passage 70', 72 will in general be provided with valve control means similar to all of the air inlets previously described.

A further vpurpose and advantage of acmitting air to the draft tube, either directly or through the runner, is the avoidance of the vibration or surging which sometimes results from the formation of eddies or cavities within the draft tube.

I claim:

1. In a hydraulic turbine the combination with means for directing the flow to the runner as in a reaction turbine, of runner vanes having their back surfaces formed to cause a separation of the flow from said baclr surfaces.

2. ln a turbine the combination with means for directing the new to the runner as in areaction turbine and imparting a whirl to said flow, of runner vanes having their back surfaces formed to cause a separation of the ow from said back surfaces.

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lso p 3. In a turbine the combination. with means for directing the flow to the runner as Viny a reaction turbine, of runner vanes havingtheir back surfaces formed to cause a separation of the flow from said back surfaces under certain conditions and tov permit the flow to contact with said surfaces under other conditions.V

4l. In a turbine the combination with means for directing the flow to the runner as in a reaction turbine, of runner vanes formed to cause the flow to separate from the back surfaces of said vanes at the inflow edge.

5. In a turbine the combination with means for directing the flow to the runner as in a reaction turbine, of runner Vvanes having projecting lips along their bach surfaces to cause the water to separate .from said surfaces.

G. In a reaction turbine the combination with means for directing the flow to the runner as in a reaction turbine, of runner vanes having their back surfaces formed to cause a separation of the flow from said back surfaces and air inlet means adjacent the runner hub for supplying air to the spaces between said flow and said back surfaces.

7. In a turbine the combination with means for directing the iow against the runner, of runner vanes having their back surfaces formed to cause `a separation of the flow from said back surfaces under certain conditions an-d to permit the flow to Contact with said surfaces under other conditions and air inlet means adjacent the runner hub for supplying air to the spaces between said flow'and said back surfaces.

8. In a turbine the combination with means for directing the 'How to the runner as in a reaction turbine, of runner vanes having projecting lips along their back surfaces to cause the water to separate from said surfaces and air inlet means adjacent the runner hub for supplying air to the spaces between sai-d flow and said back sur faces.

9. In a turbine the Combinati-on with means for directing the flow to th-e runner as in a reaction turbine, of runner vanes having their back surfaces formed to cause a separation of the flow from said back surfaces and air inlet means adjacent the runner tips for supplying air to the spaces between said flow and said back surfaces.

10. In a turbine the combination with means for directing the flow against the runner, of runner vanes having their back surfaces formed to cause a separationof the flow from said back surfaces under certain conditions and to permit the flow to contact with said surfaces under other 'conditions and air inlet means adjacent the runner tips for supplying air -to the spaces between sai flow and Said. back. Surfaces. i u

1l. In a turbine the combination with means for directing the flow to the runner as in Va-reaction turbine, of runner vanes having projecting lips along their back surfaces to cause the water to separate from said surfaces and air inlet means adjacent Y having their back surfaces formed to cause a separation of the flow from said back surfaces andair inlets adjacent th-e runner tips for .supplying air to the spaces between said flow and said back surfaces.

13. In a turbine the combination with means for directing the flow against the ruimer, of runner vanes having their back surfaces formed to` cause a separation of the flow from said back surfaces under certain conditions and to permit the flow to contact with said surfaces under otherI condi-tions and air inlet means adjacent the ruimer hub and tips for supplying air to the spaces between said flow and said back surfaces. y

lll. In a turbine the combination with means for direct-ing the flow to the runner as in a reaction turbine, of runner vanes having projecting lips along their back surfaces to cause the water to separate from said surfaces and air inlet means adjacent the runner hub and tips for supplying air to the spaces between said flow and said back surfaces.

15. In a turbine the combination with means for directing the flow against the run ner, of air supply Vmeans for admitting air to the runner surfaces and means controlling said air supply and adapted to-limit it to Vpredetermined conditions of turbine operation.

16. In a Aturbine the combination with means for directing the flowagainst the runner, of air supplymeans for admitting air to the runner surfaces andmeans controlling said air supply and adapted to limit it to predetermined load conditions of turbine operation. y

17. In a hydraulic turbine the combination with a runner having the flow under normal load conditions filling the space between successive vanes for at least a portion of the length thereof, and means for causing said flow to have a free surface between successive vanes under other load conditions so'that the reaction effect of the iiow under normalload conditions is changed to an impulse effect under other conditions.

A18. In a hydraulic turbine the combina-` tion with a runner having the flow under normal load conditions filling the space loe tween successivevanes for at least afportion of the length thereof, ,and means for cau`silo mg said flow to have a free surface between successive vanes under part gate conditions so that the reaction effect of the flow under normal load conditions is changedk to an impulse effect under part gate conditions.

19. In a hydraulic turbinev a runner having vanes formed to provide passages between them which will be filled with water for a portion of their length and for the remainder f their length will pass the flow as free jets only partly filling the spaces between said vanes.

20. In a hydraulic turbine a runner having vanes forming passages betweenthem adapted to be filled by the flow at one portion and to be only partlyfilled by the flow at another portion, so that said runner is adapted to operate at one part as a reaction turbine and at another part as an impulse turbine.

2l. In a hydraulic turbine the combination of a runner having the flow under predetermined low conditions filling the space betweensuccessive vanesfor at least a portion of the length thereof, means for caus-v ing said fiow as desired to leave a free surface between successive vanes so that said turbine is adapted to operate either as a reaction turbine or as an impulse turbine.

22. In a hydraulic turbine the combination with a ruimer of means for directing the flow thereto comprising an inner surface and an outer surface, and means for admitting air to the backs of the runner vanes comprising a substantially continuous opening around the said inner surface.

2B. In a hydraulic turbine the combination with arunner of means for directing the now thereto comprising an inner surface and an outer surface, and means for admitting air to the backs of the runner vanes comprising a substantially continuous opening around the said outer surface.

2li. In a hydraulic turbine the combination with a runner of means for directing the flow thereto comprising an inner surface and an outer surface, and means for admitting air to the backs of the runner vanes comprising a substantially continuous opening around the said outer surface at the entrance side of said ruimer.

25. In a hydraulic turbine the combination with a runner of means for directing the flow thereto comprising an inner surface and an outer surface, and means for admitting air to the backs of the runner vanes comprising a substantially continuous opening around the said outer surface in advance of said runner. n

26. In a hydraulic turbine having a sufficiently high velocity head in the' water entering the runner to reduce the pressure at the runner entrance to a value less than that of atmosphere, an opening orV openings around the inner wall of the entrance space leading to the ruimer, andl passages leading air to said opening or openings and thence to the runner.

27. In a hydraulic turbine having a draft tube containing a central core, an air passage within said core opening into the draft tube near the upstream end of the core for supplying' air to the central region of the draft tube.

28. In a hydraulic turbine having a runner and a draft tube containing a central core extending into proximity to the runner, an air passage within'said core opening into the draft tube near the upstream end of the core for supplying air to the central region of the draft tube.

29. In a hydraulic turbine having a water conduit contained within stationary walls and a runner in said conduit, meansv for admitting air into the central portion of said conduit below the runner through an opening or openings stationary with said walls.

30. In a hydraulic turbine in combination with a runner and a passage leading the water through said runner, portions of the walls of said passage being stationary, means for admitting air into the central portion of said passage below the runner through openings in a stationary portion of said walls.

3l. In a hydraulic turbine having a runner anda draft tube stationary pipe means opening into the drafttube in the central region of the draft tube below the runner and adapted to supply air to said central region.

32. In a hydraulic turbine having a runner and a draft tube stationary pipe means opening into the draft tube in the central region of the draft tube below the ruimer andadapted to supply air to said central region, and means controlling said air supply and adapted to supply air only under predetermined conditions of turbine operation. ,Y

33. In a hydraulic turbine having 4a runner and a draft tube the combination with a central core member in said draft tube below said runner, of means admitting air to the central region ofV said draft tube aroundsaid central core.

34. In a hydraulic turbine having a runner and a draft tube the combination with a central core member in said draft tube below said runner, of stationary means admitting air to the central region of said draft tube around said central core.

35. In a hydraulic turbine the combination with a runner and means for directing the fiow against the runner, of stationary air supply means for admitting air to the runner surfaces.

36. A hydraulic turbine comprising an unshrouded runner of substantially axial flow type and having a relatively small hub, means for directing the inflow to said runner as a continuous whirling column, and

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means for supplying air to said flow to maintain it fully separated from said hub.

37. A hydraulic turbine comprising an unshrouded runner of substantially axial flow type and having a relatively small hub, nieans for directing the inflow -to said runner as a'continuous whirling column, and means for supplying air to said flow to maintain it fully separated from said hub, and a draft tube recovering the velocity energy of the discharge from said runner. n

' 38. In a hydraulic turbine the combination with a turbine conduit formed by inner and outer surfaces of revolution and adapted to form the infiow into a continuous annular column around the axis, of a runner with its hub forming a portion of said inner surface of revolution and vhaving un-V shrouded blades extending from said hub, and an air supply through said outer surface of revolution'adapted to maintain the Vfiow separated from the portion of said outer. surface adjacent the tips of said blades. Y j

39. ln a hydraulic turbine having a sulficiently high velocity head in thewater entering the runner to reduce the pressure at the runner entrance to a value less than that of atmosphere, stationary means for admitting air to the entrance space leading to the runner. Y Y J 40. A hydraulic turbine adapted tooperate as an impulse turbine comprisingy a radial inflow portion, means for turningthe flow toward the axial direction, an un* shrouded runner receiving said flow, and

means supplying air to said' flow to maintain it fully separated from the back surfaces of the runner blades from the entrance )edges to the discharge edges.

41. .A hydraulic turbine adapted` to operate as an impulse turbine comprising a radial inflow portion adapted to impart a whirl to the entering flow, means for turning the. flow toward the axial direction, an unshrouded runner receiving said whirling flow, and means supplying air to said flow to maintain it' fully separated from the back surfaces of the runner blades from the entrance edges tothe discharge edges.

43. A. hydraulic turbine adapted to operate as an impulse turbine comprising an un* shrouded runner of substantially axial flow type, and having a relatively small hub, means for directing the inflowto' said runner cation with each of said jetsurfaces.

incassa Vas a solid whirling column, and means for its hub forming a portion of said inner sur`r face of revolution and having blades formed to pass the flow therethrough in separate jets having free surfaces between the jets and the back surfaces of the va'nes, and an air supply for said vrunner adapted to provide a coi'itinuous flow of air to said jet surfaces.V

45. ln a hydraulic .turbine the combination with a turbine conduit formed by inner and outer surfaces of revolution and adapted to form the inflow into a continuous annuA lar column around the axis, of a ruimer with its hub forming a portion of said inner surface of revolution and havingl blades formed to pass the iiow therethrough.- in separatej ets l having free surfaces between the jets and the back surfaces of the vanes, and an air supply exterior to said runner adapted to provide'a continuous flow of air to said jet surfaces.

46. In a hydraulic turbine the combination 'with a turbine conduit formed byinner and outer surfaces of'revolution and adapted to-form the inflow into a continuous annul-ar ycolumn around the axis, of a runner with vits l'hub forming a portion of said inner surface Vof revolution and having bladesV formed to pass the flow therethrough in yseparate jets having free surfaces between the ets and the back surfaces of the vanes,and an air space continuous around the axis and in communi- 47. ln a hydraulic turbine the combinacoluinn around the axis, of a runner with its hub forming a portion of said inner surface of revolution and having blades formed to pass the flow therethrough in separate jets Ahaving free surfaces between the jets and the back surfaces of the vaiies, an air space in communication with each'of said jet surfaces, and a velocity Vdecelerating draft tube receiving'the iiow discharged fromsaid runner and acting toconvert velocity energy into presure head so as to lower the back pressure. l

v48.l In a hydraulic turbine the combination with a ruimer having blades formed to guide lthe flow so that there is but` little change in the lvelocity of the flow relatively :130

to theblade surfaces, of means for4 admitting ilo tion witlra turbine conduit formed by innerA and outer surfaces of revolution and adapted to form the inflow into a continuous annular air to the flow adj acent said ruimer so that the flow will be permitted to part contact with the back surfaces of the blades without substantial change in velocity.

49. ln a hydraulic turbine the combination with a runner having blades adapted to guide the flow therethrough so as to permit the flow to separate from the back surfaces f the vanes, a cylinder gate controlling the flow to said ruimer, and means for admitting air to the ilow between said gate and said runner so as to cause the flow to part Contact with the back surfaces of the blades.

50. ln a hydraulic turbine the combination with an intake and runner and a transition space between said intake and runner, of a cylindrical plunger' moving in said transition space and having an annular opening in its central portion through which air may be admitted.

5l. ln a hydraulic turbine the combina tion with intake means adapted to form the flow into a whirling column, of a'runner receiving said flow and having relatively ilat blades with but little change in angle from entrance to exit so as to produce only a small amount of deflection of the stream passing through the runner, and stationary air supply means for admitting air to the runner surfaces.

52. ln a vhydraulic turbine having a sufficiently high velocity head in the water entering the runner to reduce the pressure at the runner entrance to a value less than that of atmosphere, an opening` or openings around the inner wall of the entrance space leading to the runner, and passages leading air to said opening or openings and thence to the runner and having valve means for controlling the rate of admission of air.

53. ln a hydraulic turbine the combina'- tion with an intake adapted to direct the flow against a runner, of a runner having a transverse areaof channel between successive blades which decreases through a limited portion of the length of the chan nel, and means to admit air to the backs of the blades in the portion of the channel length succeeding said limited portion.

54E. In a hydraulic turbine the combination with a runner of means for directing the flow thereto comprising an inner surface and an outer surface, and means for admitting air to at least a portion of the spaces between the vanes of said runner comprising a substantially continuous opening around the said inner surface.

55. ln a hydraulic turbine the combination with a runner of means for directing the flow thereto comprising an inner surface and an outer surface, and means for admitting air to at least a portion of the spaces between the vanes of said runner comprising substantially continuous opening around the said outer surface.

5G. ln a hydraulic turbine the combination with a turbine conduit formed by inner and outer surfaces of revolution and adapted to form the inflow into a continuous annular column around the axis while turning it to- Ward the axial direction, of a runner with its hub forming aportion of said inner surface of revolution and having unshrouded blades extending from said hub, of an air supply through said inner surface of revolution ad jacent said blades and near said axis.

57. In a hydraulic turbine, the combination with a turbine conduit formed by inner and outer surfaces of revolution adapted to form the inflow into a continuous annular column around the axis while turning it toward the axial direction, of a propeller, type runner having high relative velocity between the blades and the water and relatively light driving torque and stationary air admission ff.

f tion, said air supply control comprising connections to control the supply according to the gate opening.

- LEWIS FERRY MOODY. 

